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There is considerable concern in the numerical weather prediction (NWP) community that the Advanced Technology Microwave Sounder (ATMS) is merely being built to the noise specifications of the Advanced Microwave Sounding Unit (AMSU) and the Microwave Humidity Sounder (MHS). Since the AMSU/MHS have greatly exceeded the noise specification, the NWP community is worried that the ATMS in fact would be a step backwards. The International TOVS Study Conference-XIV Working Group on The Use of TOVS/ATOVS Data in Data Assimilation/Numerical Weather Prediction noted “The WG is concerned that the instrument specification for ATMS channel noise exceeds current AMSU performance and that the choice of polarisations may not be optimal for sounding the lower troposphere. The WG were keen to do more scientific studies to provide good evidence for the impact of different choices in microwave sounder design on microwave sounder impact in NWP. When these studies are complete, the WG will be in a stronger position to formulate a recommendation to satellite agencies concerning future microwave sounding missions” (English et al., 2005). The purpose of this paper is to document the initial results of one such study. The basic methodology of Kleespies and Watts (2006) will be used for this study.